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01-29-2012, 12:04 PM   #1
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Macro question

How many mm of tube will it take to get a M 100 F4 macro to 1:1

01-29-2012, 12:37 PM   #2
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the tubes usually come in a set of 3 --- use all three --- if you are using a film camera. If my brain works right it will be less with APS-C
01-29-2012, 01:05 PM   #3
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With a regular lens, 100mm of extension with a 100mm lens will reach 1:1. Macro lenses are a bit of a special case, since they're designed to extend quite a bit themselves. It follows that you should need somewhat less extension, or that you'll go past 1:1 using the same 100mm of extension. You'll have to shoot a tape measure or something to figure out exactly what you're getting.
01-29-2012, 01:17 PM   #4
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I have that lens and was told 50mm of tubes would get 1:1. I have found the lens is so sharp that when I get a 1:2 image I can heavily crop it and get the image I want without having to use tubes. But with tubes you can go beyond 1:1.

01-29-2012, 01:28 PM   #5
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QuoteOriginally posted by bluestringer Quote
I have that lens and was told 50mm of tubes would get 1:1. I have found the lens is so sharp that when I get a 1:2 image I can heavily crop it and get the image I want without having to use tubes. But with tubes you can go beyond 1:1.
I have 63mm of tube on it right now
This is a pic of a quarter is not cropped I think I am a little beyond 1:1
01-29-2012, 01:33 PM   #6
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the lens does 1:2 presently, and has a total extension in the focusing helix of 50mm,, when focused at infinity, the initial extension is obviously 100mm, To reach 1:1 on any lens you need a lens extension in total of 2 times focal length because 1:1 is when Image to lens distance = lens to focusing plane distance = 2x focal length.

therefore to get to 1:1, you need the lens 200mm from the focal plane. infinity = 100mm, focusing helix at min focus = 50mm, hence the correct answer is an additional 50mm of extension.

Most extension tubes come in 3 tube sets which add toi usually about 64mm,. therefore a 3 part set will give you a little better than 1:1.

In M42 the sets are shorter, and I an not sure in total it adds to 50mm, I would need to check
01-29-2012, 01:42 PM   #7
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A lot of TCs are about 25mm, so if you're trying to get exactly 50mm of extension, de-glassing a couple of them might do the trick. Measure first, to make sure they'll do what you want.
01-29-2012, 02:44 PM   #8
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QuoteOriginally posted by Lowell Goudge Quote
the lens does 1:2 presently, and has a total extension in the focusing helix of 50mm,, when focused at infinity, the initial extension is obviously 100mm, To reach 1:1 on any lens you need a lens extension in total of 2 times focal length because 1:1 is when Image to lens distance = lens to focusing plane distance = 2x focal length.

therefore to get to 1:1, you need the lens 200mm from the focal plane. infinity = 100mm, focusing helix at min focus = 50mm, hence the correct answer is an additional 50mm of extension.

Most extension tubes come in 3 tube sets which add toi usually about 64mm,. therefore a 3 part set will give you a little better than 1:1.

In M42 the sets are shorter, and I an not sure in total it adds to 50mm, I would need to check
That's correct for magnification due to extension:

Magnification = (1+ extension/focal.length.) true for m42 lenses as well.

Be careful though; newer IF lenses (Internal Focus) focus by shortening their focal length so the magnification due to extension may be greater than the equation above predicts.

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